Episodic Carbonate Deposits on the Triassic Continental Slope in Southern China

Abstract Episodic carbonate deposits on the Triassic continental slope in southern China are mainly composed of gravity‐flow limestones and contourite limestones. Gravity‐flow limestones were well developed in the lower and middle Yangtze area in the Early Triassic and in the Yunnan‐Guizhou‐Guangxi area in the Early and Middle Triassic. Five fundamental types of gravity‐flow limestones are recognized: slide limestone, debris‐flow limestone, grain‐flow limestone, turbidite limestone and rockfall limestone. They form six types of assemblage beds: slide‐debris‐flow limestones, slide‐debris‐flow‐turbidite limestone, slide‐debris‐flow‐grain‐flow‐turbidite limestone, rockfall‐debris‐flow limestone, debris‐flow‐turbidite limestone, and debris‐flow‐grain‐flow‐turbidite limestone. The first two were formed mainly in the Early Triassic slopes. The Middle Triassic slopes were characterized by widespread rockfall limestone. Growth faults, storms, earthquakes and oversteepened slopes are considered to be the probable triggers of the gravity flows.Contourite limestones appear as isolated lenses or thin and ripple‐laminated beds of grainstones occurring in hemipelagic argillaceous limestones and lime mudstones. They were formed at the base of the slope. Palaeocurrent data indicate that the contour currents are perpendicular to the slope. The contourite limestones are not as common as the gravity‐flow ones, but they are important in the reconstruction of the palaeogeographical and palaeotectonic settings in southern China.